The Application Research Of Short Block Encryption Technology Base On AES

In current, domestic prepaid electric bill solution is achieved by contact or un-contact IC card. There are obvious limits within this kind of physical transfer method: Hard to carry, easy to lose and damage; Users must go to special management department in order to add funds, which consumes time and energy; The encryption algorithms of the IC card are usually DES (Data Encryption Standard) and TEA (Tiny Encryption Algorithm), which is slow and not strong enough, may be cracked. Therefore, in order to implement adding fund without physical medium, realize security communication via unreliable channel and transfer the cipher by people, the cipher must be a decimal number with fixed length. It can't satisfy the apply demand when using the existing encryption algorithms translate the cipher to decimal number, because some decimal number would never be used. It is necessary to study and design the short block encryption based on AES.After introducing the development history, mathematics basic and the algorithm principle of AES, this thesis redesigns the four transforms of AES under the demand of practical application; designs the short block encryption based on AES; designs new algorithm about key distribution and Dynamic Key Distribution of application; prescribe the frame format of encryption communication, establish a protocol of encryption communication against unreliable channel; finally, encryption communication mode of pre-payment code meter is proposed.Within the prepaid electric bill solution project, based on the adequate advisement of the practical situation and security ratio, we developed a whole set of encryption system. The system should resolve the problem of distribution and management with key to the Symmetric-key cryptography algorithm. It integrates AES encryption algorithm, random encryption algorithm and chaos encryption algorithm together, so this system absorbs the advantage of these three algorithms. For example, the system has the feature of AES such as security (anti-crack) and efficiency; the random encryption algorithm decides encryption algorithm by parameters while our system does it by the secret key; the key is sensitive to the initial condition like chaos algorithm, which always utilizes different keys.In the end, this thesis analysises the the short block encryption's security performance and simulate the algorithm based on AES, resolves the exhaustive search problem of the short block encryption through limit the time of the cipher input by meter's user a day. All in all, the algorithm can satisfy the security needs of practical application.